The invention relates to a hand tool machine, having a housing, a motor shaft that is coupled to a drive motor, a working spindle that can be driven in a rotationally oscillating manner about its longitudinal axis, and a coupling element that can be driven rotationally by the motor shaft and has a closed guide surface that revolves about a guide axis, the guide surface being coupled, via transmission means, to at least one driver for the purpose of driving the latter.
Such hand tools are known in principle in the prior art, for example from DE 80 31 084 U1. In the hand tool known from this application, the rotation of a motor shaft generated by a motor is transmitted to an oscillating lever by means of an eccentric portion of the motor shaft. The oscillating lever is connected to a tool spindle in a rotationally fixed manner, such that a motion of the oscillating lever caused by the rotating eccentric portion results in a rotational oscillation of the tool spindle.
A transmission for generating a rotational oscillation can be configured in principle by means of such a design of an oscillation-driven hand tool.
An alternative drive for generating a rotational oscillation of a tool spindle in the case of a hand tool according to the type stated at the outset is known from DE 38 40 974 A1. In that case, a transmission lever is made to assume a wobbling motion by means of a wobble bearing driven in rotation by a motor. The transmission lever is coupled to the tool spindle by means of a sliding joint that intersects perpendicularly the longitudinal axis of a tool spindle. Owing to the wobbling motion of the transmission lever, the tool spindle, for its part, is then driven in a rotationally oscillating manner about its longitudinal axis. Since, in this case, the longitudinal axis of the tool spindle and an axis of a shaft that drives the wobble bearing are mounted at a fixed distance from one another, the transmission lever executes, relative to the longitudinal axis, a sliding motion along the sliding joint in addition to the swivelling at the same frequency. Moreover, the wobble bearing is held so as to be axially displaceable along a shaft profile of its drive shaft, in order to be able to assume, according to the turning and sliding motion of the transmission lever through and about the longitudinal axis of the tool spindle, an axial position on the drive shaft that is force-coupled to this motion.
A rotational oscillation of a tool spindle can, in principle, be effected in an alternative manner by means of such a hand tool, but only with a large number of parts and with a large amount of structural space being required, determined by the position of the elements in relation to one another, which is disadvantageous for hand tools of the type stated at the outset. The large structural space requirement is caused, in particular, by the fact that the shaft for driving the wobble bearing, on which the wobble bearing is mounted so as to be axially displaceable, is arranged perpendicularly, with a minimum distance defined by the dimensions of the wobble bearing, relative to the longitudinal axis of the tool spindle. For this reason, driving of this drive shaft by a motor whose motor axle preferably intersects the longitudinal axis of the tool spindle can be effected only with allowance for an additional transmission stage between the motor and the drive shaft of the wobble bearing. Moreover, the greatest precision is to be required primarily at those portions intended to provide for the axial displaceability of the wobble bearing on its drive shaft with simultaneous rotational driving of the wobble bearing by the drive shaft, as a result of which the production complexity is greatly increased.
Such hand tools having an oscillatory drive have multiple applications, for instance in grinding, sawing or, alternatively, also cutting of workpieces. In such cases, usual oscillation frequencies are approximately in the range of 5000 to 25000 oscillations per minute, typical swivel angles of the tool spindle being approximately between 0.5 degree and 7 degrees.
Hand tools designed in this way are highly flexible, and are suitable for many possible applications, types of use and usable tools. Owing to their compact and light form, they enable the user to adopt a great variety of gripping or working positions in relation to the hand tool or the workpiece. It has been found, however, that the handling of such hand tools can be improved in the interest of more comfortable working. In this respect, consideration is given primarily to the weight of the hand tool and to the vibration experienced by the operator.
Known from WO 2008/128804 A1 is a further hand tool according to the type stated at the outset, which has a mass balancing device for balancing out vibrations, having a stroking mass part displaceably mounted in a guide and impinged upon by an eccentric portion of a motor shaft. The stroking mass part thereby executes a sliding motion, which is directed substantially contrary to the motion of an oscillating lever about a tool spindle.
The vibrations produced by the oscillatory drive can be reduced by means of such a mass balancing device, but the production resource requirement and the weight of the hand tool machine are consequently increased and, in addition, its susceptibility to wear can increase.